"Countries with nuclear weapons are not in a position to turn to another country and say: 'You are not supposed to produce nuclear weapons,'" he said.
"Iran has consistently spoken of the fact that it is seeking to use nuclear energy for civilian purposes and that they are using uranium enrichment programmes for civilian purposes only."
"That is what Mr Ahmadinejad has told me many times before."
Mr Erdogan said he had personally warned the Iranian president about the risks of nuclear conflict in the Middle East.
"I told him I don't want to see nuclear weapons in the region, and Mr Ahmadinejad told me that they do not have an intention to produce nuclear weapons."
In February, the International Atomic Energy Agency (IAEA) said in a report that Iran's refusal to co-operate and answer questions about its nuclear programme raised concerns about the possible existence of "past or current undisclosed activities related to the development of a nuclear payload for a missile."
It also confirmed that Iran had produced 20% enriched uranium.
Tehran says it needs the more highly-enriched uranium for a research reactor producing medical isotopes, but Western powers fear it is heading towards enriching uranium to the 90% required for a weapon.
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